X-ray tube of high output



Jan. 19, 1960 B. RAJEWSKY X-RAY TUBE OF HIGH OUTPUT 2 Sheets-Sheet l FiledSept. 23, 1955 BUR/5 RAJEWSK/ Attorneys Jan. 19, 1960 B. RAJEWSKY J X-RAY TUBE OF HIGH OUTPUT 2 Sheets-Sheet 2 Filed Sept. 23, 1955 TuM BUR/.5 RAJEWSK/ United States Patent 2,922,060 X-RAY TUBE OF HIGH OUTPUT I Boris Rajewsky, Frankfurt am Main, Germany 1 Application September 23, 1955, Serial No. 536,247

Claims pricrity, application Germany September 25, 1954 8 Claims. (Cl. 313-579) This invention relates to an improved type of source for the emanation of Roentgen rays and more particularly to X-ray tubes having a high output.

it is known that the X-rays which are generated in the focal spot of the anode of an X-ray tube emanate from the focal spot in all directions so that only that portion of the emanation can be effectively utilized which is emitted in the direction toward the object to be irradiated. Consequently, a major share of the emitted X-rays remains unutilized and is absorbed, for instance, by the tube casing. Since the unutilized share of the emanated X-rays increases with the distance of the objects from the focal spot, it is advantageous to approximate the object as'closely as possible to the focal spot so as to obtain a high output or dosage yield of X-rays in the work space, i.e., the space in which the object to be irradiated is located. 'Ihis approximation between the object and the focal spot is achieved in the art, for instance, by using a hollow resonator anode tube such as described, for instance, in the patent to Cassen 2,342,789 relating to super voltage X-ray tube. In tubes of this kind, the X-rays are generated on a flat anode membrane which serves simultaneously as the ray-transmissive window of the tube and is usually cooled by a flow of coolant passing between the aforesaid window and a second outer window. In this known arrangement, almost the entire share of the X-rays directed toward the outside can be utilized; that is to say, the X-rays have a particularly high dosage output in the vicinity of the outer ray-transmissive window due to the short distance of the work space outside that Window from the focal spot.

It is, however, a drawback of this known arrangement that the work space receives its radiation only from one side so that the dosage distribution of the radiationin the work space is relatively homogeneous. Furthermore, the size of the focal spot and, consequently, the load capacity of the tube are limited by the fact that the focal spot must not be substantially larger than the object to be irradiated since, otherwise, too large a portion of the X-rays will not reach the object but by-pass the same. It has been attempted to avoid this drawback by arranging a plurality of such hollow resonator anode tubes on various sides of the work space. However, this requires a considerable amount of apparatus and correspondingly higher expenditure, apart from the fact that frequently the space available is not sufficient.

It is an object of my invention to provide the highest possible dosage yield in a geometrically limited work space.

It is another object of my invention to provide an X-ray tube having a work space which can be continuously traversed by the objects to be irradiated.

It is yet another object of my invention to provide an X-ray tube having a work space which is exposed to a substantially homogeneous irradiation and is simultaneously easily accessible.

2,922,060 Patented Jan. 19, 1960 In order to obtain the aforesaid and other objects and advantages, I have invented an X-ray tube which is provided with an anode being a large concave ray transmissive member, which vaulted surface surrounds the work space at least partially, i.e. on several sides thereof. Since the focal spot can thus be extended over a large surface surrounding the work space under optimal conditions, a large proportion of the generated X-rays can be utilized and a high load capacity of the tube can be attained.

Another advantage of a concave, vaulted anode for use in a concave anode tube resides in the fact that the anode membrane is only subjected to tensile stress.

I have found that it is preferable to arrange the cathode surrounding the anode on the side of the latter facing away from the work space. Improved results are further obtained by providing screening means on the outside of the cathode facing away from the anode. A higher load capacity of the anode is obtained by cooling the same in a suitable manner.

My invention will be better understood upon reference to the accompanying drawings in which Figure l is a longitudinal section through an X-ray tube according to the invention;

Figure 2 is a cross-section along line 2-2 in Figure 1;

Figure 3 shows another embodiment of an X-ray tube according to the invention;

Figure 4 is a sectional view along line 4-4 in Figure 3;

Figure 5 shows an arrangement wherein two X-ray tubes of the type shown in Figures 3 ,and 4 are combined to form a closed work space; and

Figure 6 shows yet another embodiment of an X-ray tube according to the invention in longitudinal section.

Referring now to the drawings more in detail wherein like reference numerals designate like parts, reference numeral 1 indicates the anode which partially surrounds the work space 8. In the embodiment shown in Figures 1 and 2 the ray transmissive anode 1 is tube shaped. An inner tube 2, of ray transmissive material, is disposed concentrically with anode 1 so as to provide a cylindrical channel 3 for the passage of a coolant. The coolant prevents excessive heating of the anode 1 under high loads. Inlet and outlet means 11 and 12 admit a coolant to, and remove the same from chamber 3. The tube 2 can be made, for instance, using aluminum, beryllium, or other similarly ray-transmissive material, in order to keep the loss of radiation as low as possible. A cathode 4 in the form of an incandescent coil is arranged about anode 1 surrounding the latter concentrically. Cathode 4 is externally screened off by means of a deflecting tube 5. The evacuated space enclosed by the tube casing 6, the insulated cathode carrier body 7, and the anode 1, can either be evacuated and sealed off in a known manner or it can be currently evacuated by a vacuum pump (not shown) which is connected to the pipe joint 9.

The filament voltage and anode voltage are supplied from sources of electric energy (not shown) by way of connecting wires 10. The voltage counterpole of the anode voltage which is preferably arranged at the casing 6 is not shown in order to simplify the illustration of the invention, nor is the Wiring of the deflecting tube 5 shown, which tube 5 is preferably charged with a negative potential against the cathode 4. However, it is also possible to insulate the deflecting tube 5 and thus completely eliminate the wiring of this tube.

A special advantage of the embodiment shown in Figures 1 and 2 resides in the fact that the X-ray tube according to this embodiment can be built of any desired length, and that the objects to be irradiated can be continuously transported through the work space 8.

The embodiment shown in Figures 3 and 4 of the drawings is distinguished from the embodiment of Figures 1 and 2 by the fact that anode 1 is of a substantially semi-cylindrical shape. X-ray tubes having anodes of this type-which show an inwardly curved anode surface, only partially surrounding'the work space, have the advantage that the objects to be irradiated can be placed on a conveyor belt for the arrangement of which there is suificient space available opposite the anode surface] The conveyor belt is indicated schematically at 14. However, the dosage yield attained in the work space 8 in this embodiment is inferior compared with that of the embodiment shown in Figures 1 and 2.

A greater dosage yield can be obtained if two'X-ray tubes of the type shown in Figures '3 and'4 are combined to surround the work space 8 tubularly as in the arrangement shown in Figure 5. The' dosage yield attained by this arrangement in the work space 8 is approximately the same as that of the X-ray tube embodiment shown in Figures 1 and 2. Furthermore, the arrangement of Figure 5 has the advantage, compared with Figures 1 and 2, that the work space 8, as well as a transporting device for the objects to be irradiated which may be disposed in the work space, are more easily accessible. 7 a

The embodiment of an X-ray tube shown in Figure 6 permits achieving a particularly high dosage yield in work space 8. As can be seen from Figure 6, anode 1 surrounds the work space 8 in the form of a dome.

The objects to be irradiated are introduced into the work space 8 through the opening 13, which is disposed laterally if the work space extends horizontally as shown in Figure 6.

The work space may also be completely enclosed by ray transmissive anode surfaces. This is achieved by combining several X ray tubes of suitably shaped anodes,

for instance, by opposing two X-ray tubes of the type 7 shown in Figure 6, to one another with their openings 13 facing each other.

The X-ray tubes according to the invention are particularly useful for radiation with X-rays requiring high X-ray dosages in a relatively short time, where a pointshaped source, or almost'point shaped source,'of 'emanation is of secondary importance. X-ray' tubes according to the invention are, therefore, applicable in medical therapy, in the biologicalfield where organisms are to be destroyed or mutated, in the chemical field where substances are to be decomposed or altered, and in subordinate techniques. These fields comprise the destruction of micro-organisms causing fermentationa'nd other deterioration of food, medicaments, objects of art, and the like; further, the testing of materials used in radiation techniques with regard to their resistance to rays and the testing of other properties of materials.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages anode is at and conditions and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

I claim;

1. In an irradiating apparatus, an X-ray tube comprising a concavo-convexX-ray transmissive anode the shape ofwhichis that of at least a portion of a substantially cylindrical surface, the concave side of said anode defining a work space exterior of the tube within which work space an article may be irradiated, and a cathode arranged on the convex' side of said anode and encompassing the same, said cathode being elongated in the direction of the axis of said substantially cylindrical surface and extending throughout substantially the length of said anode to produce a focal spot on-said anode which extends over substantially the entire surface thereof, whereby articles passed through said work space are irradiated substantially uniformly.

2. An X-ray tube as defined in. claim 1 further comprising a concavo-convex X-ray transmissive member having a shape substantially similarto that of said anode and arranged on the concave side thereof so that said anode and member form between themselves passage through which a coolant may flow.

.3.'TAn X-ray tube as defined in claim 1 further comprising screening means encompassing said cathode for vdeflecting outwardly moving electrons emanating from saidcathode.

4. In an irradiating apparatus, an X-ray tube as defined in claim 1, and conveyor means for continuously conveying through said work space that whichis to be irradiated; 1

5. 'An X-raytube as claimed in claim 1 wherein said anode is of cylindrical shape, surrounding said work space on all but two opposite sides.

6. An X-ray tube'as defined in claim 5 wherein said cathode is in the form of acoil.

7(An X-ray tube as claimed in claim 1 wherein said least a portion of a substantially semicylin- :drical shape.

8. Inani irradiating apparatus, two X-ray tubes as defined in claim .7, said tubes being positioned opposite each other so'that the two semicylindrically shaped anodes together define a cylindrical work space.

i References Cited file of this patent UNITED STATES PATENTS 2,602,751 Robinson July 8, 1952 

